Therefore, comb copolymers are already known from the prior art, in which the solubility properties can be adjusted by selection of the co-monomers in the side chains so that solubility is either provided in an aqueous system or in an organic solvent system. Thus, comb copolymers, in which the side chains are composed of polyacrylates or polyesters and are modified with phosphoric acid ester groups, amine groups, salts of amines or quaternary ammonium salts as end groups, and whose solubility either in water or in an organic solvent can be adjusted by selection of the co-monomers in the side chains, are described in U.S. Pat. No. 6,472,463 or DE-C-60 016 758. However, a solubility both in an aqueous medium and in an organic solvent cannot be adequately adjusted herewith, and therefore the use of such comb copolymers as wetting and dispersing agents, e.g. in colour filter production processes, can only lead to excessively long processing times.
Comb copolymers based on styrene/maleic anhydride resins (SMA resins), which have polyether side chains but no adhesion groups, are described in U.S. Pat. No. 6,406,143 or in U.S. Pat. No. 6,528,593. These dispersing agents have the disadvantage that they cannot adequately stabilise organic pigments in formulations containing solvent.
The use of comb copolymers based on SMA resins disclosed in U.S. Pat. No. 6,423,785 that have polyether side chains and can be modified with amine oxide groups as wetting and dispersing agents does not always meet the requirements for a dispersion of pigments that is stable in storage.
This also applies to the use of comb copolymers based on SMA resins that can have polyether side chains and amino groups, which are converted to salts with unsaturated carboxylic acids (cf. U.S. Pat. No. 7,078,464), since the described adhesion groups do not represent adhesion groups that are suitable for all application areas. An additional consideration with the use as wetting and dispersing agents is that as a result of salification with an unsaturated carboxylic acid there is the risk of polymerisation and thus an undesirable salification of the wetting or dispersing agent during storage.
Therefore, on the basis of the prior art there was a need to make wetting and dispersing agents available that besides an excellent stabilisation of solid dispersions, in particular pigment dispersions, have an excellent solubility both in aqueous media and in organic media in order to meet the increased requirements for wetting and dispersing agents in many fields of application such as universal tinting pastes, pigment surface modification for the production of easy to process pigments or colour resists for colour filters. In particular, in the case of these requirements a very low viscosity of the pigmented paint is also required, which can generally only be achieved with a wetting and dispersing agent with an extremely good stabilisation of the pigment dispersion also during storage.
Therefore, it was an object of the present invention to provide comb copolymers, which are highly soluble in aqueous media as well as in organic media and with which solid dispersions that are low-viscosity and stable in storage are obtained as wetting and dispersing agents.